A lens is an electronic device that can focus a planar wave front of EM waves to a focal point or, conversely, collimate spherical waves emitting from a point source to plane waves. Such fundamental characteristics are widely used in various applications, such as communication, imaging, radar, and spatial power combining systems. For example, in millimeter-wave frequency bands that fifth generation (5G) communication standards may employ, lenses have been paid considerable attention as a potential solution to overcome limits in gain and beam steering capabilities of antennas operating in such frequency bands.